EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Discussions on Talking Machines of British or European Manufacture
pallophotophone
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EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by pallophotophone »

Hello !

I've just finished combining parts from 2 Garrard motors to make one good one. A model AC 7. And it performs splendidly.
But I had to get inventive when having to concoct a set of 3 rubber washers used to isolate the motor mounting plate from the main top plate. The 60 cycle hum from the motor isn't too bad, but I can't get past the idea that it could be better if I could find modern and correct hardness replacements for the now old and hard as a rock originals. And I have what I'd call 3 metal spacer washers left over and I can't remember where they go. They were on the motor to begin with. Everything in /on the motor or mountings are correctly tight so there is nothing loose to cause vibration.

About the 2 spring soundbox gaskets. What I have in it now is , I believe too large an O.D. which holds the diaphragm in a vise like grip. What size did EMG use ? I have some other sizes purchased from a British dealer , but I'd rather not have to take this apart too many times to experiment.

A little about this machine. It was owned by Professor Walter Welch, Co author of "From Tinfoil To Stereo" and founder of the Syracuse University Audio Archive at Syracuse University. I worked with him on some of his machines, including the EMG, and electronics over the years I was employed at S.U. After Professor Welch's passing, I purchased the machine from his daughter where it now holds a prominent place in my collection. It has a horn with a 28 ½ inch opening and has very little sag, it does show it's age, a little. I retired in 2020.

Many Many Thanks in advance !!

Bob Hodge

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emgcr
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by emgcr »

Hello Bob,

Your Mk IX EMG sounds most interesting but it would appear to be a mix of models. The Mk IX had a horn featuring a final bell diameter of 22” whereas the Xa had a diameter of some 28 ⅝”. Spigot sizes were identical for all EMG models thus horn sizes could be swapped with ease. If your horn has a slim joint casting at the knuckle (where the two sections of the aluminium casting join) this will confirm it to be the Mk Xa. The Xb had a thicker band at this point and a final diameter of 29 ½”. It was by no means unknown for customers to upgrade their instruments in contemporary days as development advanced. The larger the final diameter to air, the greater the bass reproduction. The exponential flair was identical in all models.

Regarding the Garrard AC7 motor, I do not have a photo but you may find the attached images of various Garrard models (click on image to clarify/enlarge) will answer your query about the surplus steel washers ? I think it is a question of experimentation and personal satisfaction regarding the hardness/softness of the rubber washers themselves. There are many types cheaply available.

The outside diameter of hollow rubber tubing (suitable for both the 2-spring and 4-spring EMG soundboxes) is usually about 0.1275” (3.24mm) which is standard for (UK) bicycle tyre valves. Cut lengths on a slight angle (to compensate for the different lengths of the outer and inner edges when in circular form) and a little longer than the nominal circumference to introduce slight joint pressure which will produce the all-important air-tight environment internally. You are quite right about the lateral pressure on the diaphragm---best results are obtained from the gentlest exertion consistent with air-tightness.

Many thanks for the interesting history and background of your instrument---another one to add to the list of extant examples.

Photographs would be very helpful and much appreciated.

Best wishes,

Graham
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IainW
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by IainW »

Graham, do you think it is necessary to put ballast into the bottom of the case or strengthen the side extension if fitting a larger size horn to a Mark 9 gramophone or is the original structure well capable of supporting the extra out of balance loads imposed?
Iain

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emgcr
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by emgcr »

Excellent question Iain. The Mk IX case (without ballast) is quite capable of supporting even an Oversize horn on the cantilevered outrigger to the left hand side of the case but subject to one important proviso. The larger horn should be mounted in such a way across the width of the case so that the weight is taken where all possibility of tipping is dissipated. Years ago I used to reinforce the normal position of the overhung Mk IX support with wedges to allow use of the Oversize horns (slightly nose-heavy) without toppling, which system worked well until one evening they became accidentally dislodged with disastrous consequences. One learns from one's mistakes (hopefully)................! One also suspects that EMG quickly saw the good sense of having a conduit outlet at the centre of the case for all the (heavier) Mk Xs.

The attached photos (including some of the usual suspects !) make the point :
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anchorman
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by anchorman »

You can get 30A durometer silicone rubber tubing from McMaster-Carr in both ⅛” and 3mm diameter. I’ve used it successfully in rebuilding a few soundboxes, and it’s basically what my friend the professional reproducer repairman uses.

Regarding your motor washers/grommets, McMaster Carr probably has something suitable. If you can’t find something the right size you might find someone with a laser cutter who can cut rubber sheet for you to make the correct size parts.

I have family in central NY, and would love to come and see your machine sometime when I’m up visiting them!

anchorman
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by anchorman »

McMaster-Carr part numbers to save you looking:

5054K801 35A white silicone rubber tubing 3mm diameter
5236K502 35A white silicone tubing ⅛” diameter

They have lots of other good stuff too. If you don’t want to buy this much tubing, contact Wyatt Markus, and he’ll sell you a shorter length. I could also send you a short length of each at no cost if you send me your address. I don’t know that I’ll ever use up the 25 feet that I bought. I like servicing reproducers, but not *that* much. :lol:

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Orchorsol
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by Orchorsol »

We all have our own preferences of course, but I and pretty much all other EMG/Expert enthusiasts I know greatly prefer the beige natural rubber vintage bicycle valve tubing that Graham mentioned above.

Another important point (just in case it's not clear) is that EMG and Expert soundboxes should not be screwed up tight shut. The gap between the halves of the soundbox shell is one of the several means of tuning. Most of us introduce thin rubber washers (often a slice cut from the gasket material) on the screws between the halves, as well as under the screw heads and the nuts.
BCN thorn needles made to the original 1920s specifications: http://www.burmesecolourneedles.com

Youtube channel: https://www.youtube.com/channel/UCe4DNb ... TPE-zTAJGg?

IainW
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by IainW »

Thanks for your explanation Graham. I never gave it much thought before, but just assumed that the curved shape of the EMG Mk X horns was designed so that the centre of gravity was over the spigot (but of course I may be wrong) As the larger horns were introduced did the rearward section of the horn project further back to maintain the centre of gravity or did the C of G move significantly towards the enlarged bell and hence introduce the toppling moment.

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emgcr
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by emgcr »

I am sure you are right and the general idea would indeed have been to aim for the C of G to be roughly over the spigot. The swan's neck design is attractive so there were probably cosmetic considerations as well. The spigot was made of strong bronze, rather than brass, as the diameter and wall-thickness was not great. However, most of the weight of Mk Xa and Xb horns is in the aluminium castings thus the extent of the bell does not make a huge difference to the balance. In my experience most EMG horns are slightly nose-heavy but the Mk Xa, Xb and Xb Oversize examples never suffer from the dreaded droop thanks to the extensive castings (all of similar dimensions) at the high stress points---excellent design. Earlier swan's neck horns---Mk IX and X---did droop/snap due to the lack of adequate metal structure .

Expert, by contrast, produced "up-and-over" horns with a greater preponderance of lightweight paper but minimal metal castings (plus metal under-gussets) the lighter of which have survived well. Many, however, were too heavy and do suffer from droop at the greatest stress points even though the strength of the bell mouth was augmented by an incorporated metal ring. The design cannot be said to be the best from a structural point of view. However, spigots were much larger in diameter and therefore stronger and made from thick-wall aluminium.

pallophotophone
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Re: EMG Mark 9 w/ Garrard Ac Motor and 2 spring soundbox

Post by pallophotophone »

Thank You one and all for the great information. Pictures will be forthcoming just as soon as I can figure out how to post them.

If I've located it correctly, the machine has a serial number of 1087, located at the uppermost place in the wood, just above the metal Garrard motor platform.

I recalled that have a "London" brand valve based portable machine in my attic and it uses the AC 6 style motor as the EMG, so I can use it to determine the correct placement of the rubber washers. It looks as though it was never disassembled. By your leaflet image, the 3 metal spacer washers appear to be used to adjust the motor/turntable height as necessary. It's fine without them. They were probably used to take up space on the 3 fixing bolts, underneath the motor sub mount plate, on the 3 nut/bolt assemblies.
But I still enjoyed seeing the Garrard leaflet and what they had to offer. But that leads me to another question. I have a 201b turntable w/ 78 and 33 ⅓ speed levers on it. Did EMG ever put this in their machines ? It looks as though it was built like a tank. If the BBC used them, it must have been top notch.

I couldn't agree more about the center of gravity issue with the horn. And have always used the diagonal position for it.
Wish I could have been at your garden listening party with a few select discs !! How perfectly splendid !!
Do you remember what was playing in that picture? I can easily hear Eric Coates, Sir Henry Wood, Geoffrey Toye, Sir Edward Elgar, Percy Fletcher or Sir Thomas Beecham holding forth. Or any host of fine British performers, In both popular and classical veins. Far too many to try to list.

Anon,

Bob Hodge
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Last edited by pallophotophone on Wed Jun 22, 2022 3:39 pm, edited 1 time in total.

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